Allied Telesis AT-S62 - Manual (Page 255)

AT-S62 Menus Interface User’s Guide
Section II: Advanced Operations 255
Note
QoS is only performed on packets which are switched at wirespeed.
This includes IP, IP multicast, IPX, and Layer 2 traffic within VLANs.
The QoS functionality described by this chapter sorts packets into
various flows, according to the QoS policy that applies to the port the
traffic is received on. The switch then allocates resources to direct this
traffic according to bandwidth or priority settings in the policy. Each
policy is built up out of traffic classes, flow groups and classifiers. In
summary, to configure QoS:
❑ Create classifiers to sort packets into traffic flows.
❑ Create flow groups and add classifiers to them. Flow groups are
groups of classifiers which group together similar traffic flows.
You can apply QoS prioritization to flow groups and/or replace
the traffic’s DiffServ Code Point.
❑ Create traffic classes and add flow groups to them. Traffic classes
are groups of flow groups and are central to QoS. You can apply
bandwidth limits and QoS prioritization to traffic classes, and/or
replace the traffic’s DiffServ Code Point.
❑ Create policies and add traffic classes to them. Policies are groups
of traffic classes. A policy defines a complete QoS solution for a
port or group of ports.
❑ Associate policies with ports.
Note
These steps are listed above in a conceptually logical order, but the
switch cannot check a policy for errors until the policy is attached to
a port. You can simplify error diagnosis by determining your QoS
configuration on paper first, and then entering it into the switch
starting with classifiers.
Policies, traffic classes, and flow groups are created as individual entities.
When a traffic class is added to a policy, a logical link is created between
the two entities. Destroying the policy will only unlink the traffic class,
leaving the traffic class in an unassigned state. Destroying a policy will
not destroy any of the underlying entities. Similarly, destroying traffic
classes will simply unlink flow groups and destroying flow groups will
simply unlink classifiers.